The present invention relates to microorganisms including bacterial strains capable of degrading indigo and indigo carmine. The present invention also relates to enzymes produced by these microbial strains which are capable of degrading indigo and indigo carmine.
Indigo is a well known dark blue dye. It is commercially available as a crystalline powder having a bronze luster. Indigo is insoluble in water, alcohol, ether, and dilute acids. It is slightly soluble in chloroform, aniline, and other nonpolar organic solvents. The 5,5'-disulfonate derivative of indigo is also a blue dye known as indigo carmine. In contrast to indigo, indigo carmine is soluble in water. The chemical structures of indigo and indigo carmine are shown below. ##STR1##
As in the case of many other dyes, the intense coloring of indigo and indigo carmine is due to the .pi. conjugation system. Rupturing the .pi. conjugation system of these compounds will result in decolorized products. Furthermore, because the .pi. conjugation system of indigo and indigo carmine is the same, substances which decolorize indigo are expected to decolorize indigo carmine as well.
Indigo is used extensively as a dye by the textile industry, particularly for denim products. The annual world production of indigo exceeded 14,000 tons by 1988 (Ref: American Dye Stuff Reporter, vol. A14, p. 154 [A-06141]). In many Asian countries where denim is manufactured, such as Hong Kong, Taiwan, China, etc., indigo presents an environmental problem. For example, about 4,000 tons of indigo are imported per year into Hong Kong, of which about 350 tons per year are consumed. A significant fraction of the remaining indigo is discharged into the environment by hundreds of textile and dyeing factories. Thus, indigo is a major man-made pollutant in the water streams of many Asian countries where denim is produced.
In recent years, efforts have been made to isolate microorganisms which are capable of degrading pollutants. Among these are several microorganisms which have been isolated because of their ability to degrade dyes. Microbes capable of degrading azo dyes have been identified by Horitsu et al., 4 Eur. J. Appl. Microbial 217-224 (1977); Idaka et al., 24B. J.S.D.C. 91-94 (1978); Kulla in Microbial Degradation of Xenobiotics and Recalcitrant Compounds, by Leisinger, et al., 389-399, Academic Press, London (1981); and Yatome et al, 13 NA J.S.D.C. 97:166-169 (1981). The initial strains were isolated for their ability to degrade food azo dyes (see Childs et al., 16 Biochem. Pharmacol. 1551-1561 (1967) and Roxon et al., 4 Fd. Cosmot. Toxicol. 419-426 (1966)). In later years, several investigators have identified species of Pseudomonas, Bacillus, and Flavobacterium able to degrade textile azo dyes. See Wilcox et al., 21 Forest Products Journal 50-52 (1970); Horitsu et al., supra; Idaka et al., supra; Yatome et al., supra; and Kulla et al., supra. More recently, it was found that triphenyl methane and crystal violet can be degraded by the yeast Rhodotorulae and the fungus Phanerochaete. See Kwasmiewska, 34 Bull. Environ. Contam. Toxicol. 323-330 (1985), and Bumpus et al., 54 Appl. Environ. Microbial. 1143-1150 (1988).
Until now, however, there have been no reports or suggestions for isolating a microorganism, or an enzyme produced by a microorganism, capable of degrading the dyes indigo and indigo carmine.
Accordingly, it is an object of the present invention to isolate one or more microorganisms which are capable of degrading the dyes indigo and indigo carmine.
It is a further object of the invention to isolate the enzymes produced by these microorganisms which enzymes are capable of degrading the dyes indigo and indigo carmine.
It is a further object of the present invention to provide a method for treating waste water containing the dyes indigo and indigo carmine by bringing the waste water into contact with microorganisms or enzymes produced by microorganisms which are capable of degrading indigo and indigo carmine.
It is a further object of the present invention to provide a method for bleaching a substrate, such as a denim, dyed with indigo or indigo carmine by treatment of the substrate with a suspension of a microorganism or an enzyme extracted from a microorganism capable of degrading indigo and indigo carmine.